1. Field of the Invention
This invention relates to layout tools for framing squares and particularly to layout tools that have alignment mechanisms and markings, which attach to framing squares.
2. Description of the Prior Art
Framing squares are a ubiquitous tool of carpenters and other builders. This tool is used to layout rafters and stair stringers as well as many other functions. In the case of rafters and stairs, many calculations are required, depending on the type of rafter (e.g., hip rafter, valley rafter, etc.) and stairs. It takes a lot of experience to do this work properly and consistently. Once the calculations have been made, the carpenter uses the framing square to mark construction material with the lines used to cut the rafter or stair stringers. Again, care must be used to ensure that the cut lines are correct as time and material are wasted once a board has been cut improperly. Another problem with using the square is that rafters and stair stringers require many layout marks. A square, by itself, must be positioned, and aligned with the proper measurements each time a cut is made; this takes time and adds to the possibility of error.
Over the years, people have developed tools that can assist the carpenter in making these measurements and cuts. One such example is found in U.S. Pat. No. 935,067 To Taylor. This too shows a small square that has a groove cut into each major axis of the square. A straight rule, with two grooves cut in it is attached to the square and held by to fasteners that are placed through the grooves in both the rule and the square. The rule can then be positioned across the square and locked into the measured lengths so that repeated marks can be made with minimal error. The problem with this device is that it requires the square to have the grooves into which the fasteners are secured. Moreover, to use the square for other applications, the rule must be removed, which takes time. Another tool that helps is found in U.S. Pat. No. 6,070,334 to Pretsch, Jr. This design is a simple straightedge that is secured to a common framing square so that it forms a straight edge that can be abutted against a board so that the proper cut lines can be drawn. This tool is better than the Taylor device in that it can be used on a standard framing square. However, the user must make the calculations as before; thus, there is limited advantage to using this tool. Another tool is found in U.S. Pat. No. 7,197,833 to Ekern. In this design, the tool has a pair of groves cut through the tool. The framing square is slid into these grooves and placed in the proper position. Then, the tool is locked in place and the tool can be used as a straight edge. One advantage of the Ekern tool as compared to the Pretsch, Jr. tool is that, because of the body groove, the tool has a body on both the top and bottom of the square. This allows the tool to the placed against the board above or below the top surface of the board. However, as before, this tool still requires the user to calculate the angles and determine the position of the straight edge on the square as before.